Method and composition for reducing postsurgical adhesions

ABSTRACT

A process and compositions for reducing post-surgical adhesion formation/reformation in mammals following surgical injury to the peritoneal or pleural cavity or organs situated therein. Both aqueous and non-aqueous compositions comprising a polyoxyalkylene block copolymer are applied to injured areas of the peritoneal or pleural cavity or organs situated therein subsequent to surgical injury.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to methods and compositions forreducing postsurgical adhesions in the abdominal or thoracic cavity ofmammals.

2. Description of the Prior Art

There is a need for a method and composition suitable for use inpreventing adhesion formation/reformation in mammals following surgicalinjury to the peritoneal or pleural cavity, or organs situated therein.

According to Ellis in a reviewed entitled "The Cause And Prevention OfPost-operative Intraperitoneal Adhesions" in Surgery, Gynecology andObstetrics for September 1971, volume 133, pages 497-509, at pages502-503, the prevention of adhesions has been the subject of an enormousamount of work since the beginning of this century. According to Ellis,these attempts have included means of preventing the fibrin-coated wallsof the intestine from reaching each other by distending the abdomen withoxygen or filling the abdomen with saline solution, paraffin, olive oil,lanolin, concentrated dextrose solution, macromolecular solutions of allsorts, and silicones.

Caspi, Halperin, and Bukovsky in an article entitled "The Importance ofPeriadnexal Adhesions in Reconstructive Surgery for Infertility"appearing in Fertility and Sterility for March 1982, volume 31, number3, pages 296-300, at page 299 indicate that despite experimental andclinical efforts in the prevention of adhesion formation followingsurgery, no major advances have thus far been achieved. The authorsdiscuss the use of post-operative intraperitoneal installation of amixture of hydrocortisone acetate, promethazine, and ampicillin. As analternative method of treatment, a low molecular weight dextran (aglucocorticoid) was also instilled intraperitoneally in another group ofpatients. The authors conclude that the intraperitoneal installation ofhigh doses of glucocorticoids combined with early hydrotubations seemsto be a worthwhile method.

Musich and Behrman in an article entitled "Infertility Laparoscopy InPerspective: Review of 500 Cases" appearing in The American Journal ofObstetrics and Gynecology for June 1, 1982, pages 293-303, at page 300in the discussion section of the article disclose that there is a needto prevent adhesions subsequent to surgery in view of a study of 35patients which indicated that 30 of these patients having serioustuboplasties had severe adhesions, one-third of which were judged to beinoperable.

High molecular weight dextran either alone or in combination withdextrose has been used in the prevention of peritoneal adhesionssubsequent to surgery. Dextran is clinically standardized to a lowmolecular weight of about 75,000 by partial hydrolysis and fractionalprecipitation of the high molecular weight particles which normally havemolecular weights of up to 200,000. Dextran is a polymer of glucosewhich has a chain-like structure and is produced from sucrose byLeuconostoc bacteria. In articles appearing in Fertility and Sterility,volume 33, number, 6, June 1980, pages 660-662, Holtz, Baker, and Tsaiand volume 34, number 4, October 1980, pages 394-395, by Holtz andBaker, results are reported of the adhesion reducing effects of a 32%(aqueous) solution of dextran 70 containing 10% dextrose (sold under thetrade name HYSKON by Pharmacia, of Piscataway, N.J.). Holtz et al.postulate several mechanisms of action in the prevention of peritonealadhesions utilizing HYSKON including a simple mechanical separation ofadjacent surfaces, termed a hydroflotation effect.

Project coordinator diZerega and several contributors have reported theresults of a large study in an article entitled "Reduction ofPost-operative Pelvic Adhesions with Intraperitoneal 32% Dextran 70: AProspective, Randomized Clinical Trial" in Fertility and Sterility,volume 40, number 5, for November 1983, pages 612-619. The authors, atpage 618, indicate that the use of Dextran intraperitoneally haslimitations such as the reported tendency of HYSKON to support bacterialproliferation and concern over the anaphylactoid potential of dextran.In addition, the benefit of Dextran 70 in preventing post-operativeadhesions was shown to be limited to the more dependent regions of thepelvis.

Borten and Taymor in Obstetrics and Gynecology, volume 61, number 6,June 1983, pages 755-757 report in an article entitled "RecurrentAnaphylactic Reaction to Intraperitoneal Dextran 75 Used for Preventionof Postsurgical Adhesions". These authors indicate that anaphylacticreaction to Dextran administered intravenously is well documented andreport such a reaction after intraperitoneal administration of Dextran.

Linsky in The Journal of Reproductive Medicine for January 1987, pages17-20 in an article entitled "Adhesion Reduction in the Rabbit UterineHorn Model Using an Absorbable Barrier, TC-7". These authors report thatthe use of a resorbable fabric barrier provides a significant reductionin post-operative adhesion formation and that no gross remnants of thefabric barrier material were noted, subsequent to initial placement,after a two week period.

Oelsner et al. in The Journal of Reproductive Medicine for November1987, volume 32, number 11, pages 812-814, reported results of acomparison of sodium carboxylmethyl cellulose, 32% dextran 70, andcondroitin sulfate to prevent the formation of postoperative adhesionsin the rabbit uterus. The authors report superior results withcondroitin sulfate which is described as a member of a family ofbiochemical compounds referred to as glycosaminoglycans (formerly termedmucopolysaccharides), to which hyaluronic acid, heparine sulfate andheparin also belong.

The use of ethylene oxide/propylene oxide block copolymers assurfactants for use in surgical scrub solutions and the topicalapplication of 10% solutions of these copolymers to wounds is describedin Edlich et al in the Journal of Surgical Research, volume 14, number4, April 1973, pages 277-284. The test results indicate that thecopolymers having an ethylene oxide:propylene oxide ratio of 4:1 provideless inflammatory response in a wound to which the copolymer is appliedin comparison with a copolymer having an ethylene oxide:propylene oxideratio of 1:4. There is no indication in Edlich et al or any prior artthat such copolymers are useful in reducing post-operative adhesions.

SUMMARY OF THE INVENTION

Compositions and a process are disclosed for reducing post-surgicaladhesion formation/reformation in mammals following surgical injury tothe organs of the peritoneal or pleural cavity. Both aqueous andnon-aqueous compositions comprising a polyoxyalkylene block copolymerare useful. Non-aqueous compositions can include a physiologicallyacceptable carrier liquid or can include a low molecular weightpolyoxyalkylene block copolymer, having a molecular weight of less than5000, in combination with a high molecular weight polyoxyalkylene blockcopolymer. The concentration of the block copolymer can be adjusted inthe useful compositions of the invention to take advantage of gelationproperties of certain polyoxyalkylene block copolymers. For instance,certain concentrations of aqueous solutions of certain of said blockcopolymers form clear gels at mammalian body temperatures but areliquids at ambient temperatures. Subsequent to deposition of thecompositions of the invention in the peritoneal or pleural cavity of amammal, the polyoxyalkylene block copolymer is absorbed by the tissueswith which it is in contact and the block copolymer is eventuallyexcreted in a non-metabolized form, mainly in the urine.

In addition to functioning as a means of reducing post-operativeadhesion formation/reformation in mammals following surgical injury tothe peritoneal or pleural cavity or organs situated therein, thepolyoxyalkylene block copolymer is believed to provide an environmentsurrounding the surgical injury which accelerates the regrowth rate ofthe injured tissue. For instance, the polyoxyalkylene block copolymercan be instilled within the uterine cavity as a distending medium duringdiagnostic or operative intrauterine endoscopic procedures. Thisapplication has two advantages. First, since certain aqueousconcentrations of the preferred polymers form a clear gel, their use iswell suited for visualization of the uterine cavity. Second, since theseaqueous solutions form a clear gel at body temperature, the use of saidsolutions to separate the uterine cavity walls will diminish or preventpost-surgical adhesion formation.

Optionally, the polyoxyalkylene block copolymer can be utilizedadvantageously in combination with bacteriostatic or bactericidalagents, fibrinolytic agents, and agents effective in preventingleucocyte migration into the area of surgical injury.

DETAILED DESCRIPTION OF THE INVENTION

A process and compositions are disclosed for reducing post-operativeadhesion formation/reformation in mammals following surgical injury tothe peritoneal or pleural cavity or organs situated therein. In thisspecification and claims, the terms "peritoneal" and "abdominal" cavityare used as synonyms, as are the terms "pleural" and "thoracic" cavity.Both aqueous and non-aqueous compositions comprising at least onepolyoxyalkylene block copolymer are useful in the process of theinvention. The compositions can include at least one of a bacteriostaticor bactericidal agent, an agent effective in preventing leucocytemigration into the area of surgical injury, and a fibrinolytic agent.

The preferred aqueous compositons are prepared at concentrations so asto take advantage of the gelation properties of certain of said blockcopolymers. When certain of the polyoxyalkylene block copolymers of theinvention are present in aqueous solutions at concentrations preferablyof about 15% to about 30% by weight, such compositions can provideliquid compositions at ambient temperatures or below which revert to gelcompositions upon contact with living mammalian tissue.

Alternatively, useful compositions of the invention include aqueouscompositions comprising at least one polyoxyalkylene block copolymerwhich does not form gels as well as non-aqueous compositions comprisingat least one polyoxyalkylene block copolymer in combination with aphysiologically acceptable non-aqueous carrier liquid. It is believedthat both the non-aqueous compositions of the invention and the aqueouscompositions of the invention which do not form gels upon contact withliving mammalian tissue function to prevent the formation/reformation ofadhesions subsequent to surgical injury by a mechanism of action whichhas been termed in the prior art "hydroflotation".

Thus the injured tissues are prevented from contacting adjacent tissuesby the means of the inclusion of a foreign fluid in the peritoneal orpleural cavity. With respect to those aqueous compositions of theinvention which are chosen from polyoxyalkylene block copolymers of theinvention which when prepared at suitable concentrations form gels uponcontact with living mammalian tissue, it is believed that the mechanismof action to prevent the formation/reformation of adhesions is, inaddition to hydroflotation, properly characterized as the result ofseparating the adjacent mammalian tissues by a firm, adherent gelcoating.

The polyoxyalkylene block copolymer compositions of the inventioninclude at least one block copolymer as below defined, optionally incombination with at least one of an adjuvant such as a humectant, abactericide, a bacteriostatic agent, an agent to prevent leucocytemigration into the area of surgical injury, and a fibrinolytic agent.The copolymer is applied to injured tissue in a major amount incombination with a minor amount of said adjuvant. Useful humectantsinclude, but are not limited to glycerin, propylene glycol, andsorbitol. Useful bactericides which can be administered in admixturewith the aqueous or non-aqueous compositions of the invention includeantibacterial substances such as B-lactam antibiotics, such ascefoxitin, n-formamidoyl thienamycin and other thienamycin derivatives,tetracyclines, chloramphenicol, neomycin, gramicidin, bacitracin,sulfonamides; aminoglycoside antibiotics such as gentamycin, kanamycin,amikacin, sisomicin and tobramycin; nalidixic acids and analogs such asnorfloxacin and the antimicrobial combination offludalanine/pentizidone; nitrofurazones, and the like. Antihistaminicsand decongestants such as pyrilamine, cholpheniramine, tetrahydrazoline,antazoline, and the like, can also be used in admixtures as well asanti-inflammatories such as cortisone, hydrocortisone, beta-methasone,dexamethasone, fluocortolone, prednisolone, triamcinolone, indomethacin,sulindac, its salts and its corresponding sulfide, and the like.

Useful leucocyte migration preventing agents which can be used inadmixtures include but are not limited to silver sulfadiazine,acetylsalicylic acid, indomethacin, and Nafazatrom. Useful fibrinolyticagents include urokinase, streptokinase, tissue plasminogen activator(TPA), and acylated plasmin. The block copolymer compositions of theinvention comprise:

at least one polyoxyalkylene block copolymer of the formula

    Y[(A).sub.n --E--H].sub.x                                  (I)

wherein A is a polyoxyalkylene moiety having an oxygen/carbon atom ratioof less than 0.5, x is at least 2, Y is derived from water or an organiccompound containing x reactive hydrogen atoms, E is a polyoxyalkylenemoiety constituting at least 60% by weight of the copolymer, n has avalue such that the average molecular weight of A is at least about 500to about 900, as determined by the hydroxyl number of a hydrophobe baseintermediate,

    Y[(A).sub.n --H].sub.x                                     (II)

and the total average molecular weight of the copolymer is at least5000.

Post-operative pelvic adhesions have been associated with infertility.Significant periadnexal adhesions have been found, as reported by Musichand Behrman, as previously cited, upon laparoscopy in 72% of 106patients having unexplained infertility who had previously undergonevarious pelvis surgical procedures. Prevention of such adhesions hasbeen proposed in the prior art by treatment with aqueous dextransolutions of low molecular weight. The prior art use of aqueous dextransolutions (i.e., dextran 70 at 32% solids) has shown adverse reactionsand little or no reduction of post-operative pelvic adhesions.

In addition, an oxidized cellulose fabric barrier (sold under the tradedesignation TC-7 by Johnson and Johnson Products, Inc., New Brunswick,N.J.), which is resorbable subsequent to utilization, has been used inthe prior art as a treatment to prevent adhesions to the peritoneum bypreventing abutting injured organ surfaces from making contacttherewith. Chondroitin sulphate solutions have also been proposed forintraperitoneal use in the prevention of adhesions in rabbits. Each ofthese proposed methods of avoiding post operative adhesions havedisadvantages which are overcome by the method of the present invention.

The mechanism of action of all of these treatments is proposed to be theresult of the persistent separation of adjacent surgically injuredsurfaces thus permitting healing to occur without the formation offibrinous bands between abutting surfaces which are characterized asadhesions. For instance, upon injury to the peritoneum there results anoutpouring of a serosanguinous exudate which is of a proteinaceousnature. This fluid subsequently coagulates, producing fibrinous bandsbetween abutting surfaces that become subsequently organized byfibroblast proliferation to produce collagenous adhesions. This processis thought to be initiated and well advanced within the first three dayssubsequent to surgical injury.

The polyoxyalkylene block copolymers which are utilized in thecompositions of the invention can be viscous liquids, pastes, orgranular solids. Where the copolymers are pastes, they can be used aloneor in admixture with an optional humectant or low molecular weightpolyoxyalkylene block copolymer having a molecular weight of less than5000. Mixtures of granular block copolymers with at least one of saidlow molecular weight block copolymers or said viscous liquid blockcopolymers are also useful. A physiologically acceptable non-aqueouscarrier or water can also be optionally added. Preferably, thecopolymers, which are viscous liquids, are used in combination withwater as a carrier or a non-aqueous carrier.

When the compositions of the invention are used in combination withwater as a carrier, preferably the aqueous solutions have a blockcopolymer concentration which provides a free flowing liquid at ambienttemperatures which gels upon contact with living mammalian tissue.Generally, the copolymers which are useful are selected from thosedefined above in formula I. Generally, the copolymer is selected fromthose copolymers which contain at least about 60% by weight, preferablyat least about 70%, by weight and most preferably at least about 80% byweight of the residue of ethylene oxide (polyoxyethylene moiety).Generally, said copolymers have a total average molecular weight of atleast about 5000, and form a gel at mammalian body temperature, when inan aqueous solution generally at a concentration of about 10 to about40%, preferably about 15 to about 30% by weight and most preferablyabout 18% to about 25% by weight.

The proportion of carrier used is about 60% to about 90%, by weightpreferably about 70% to about 85%, by weight and most preferably about75% to about 82% by weight, based upon the total weight of thecomposition of the invention. Useful polyoxyalkylene block copolymerswhich will form gels in such aqueous solutions can be prepared using ahydrophobe base (such as A in Formulas I and II) derived from propyleneoxide, butylene oxide, or mixtures thereof. These block copolymers andrepresentative methods of preparation are further generally described inU.S. Pat. Nos. 2,677,700; 2,674,619; and U.S. Pat. No. 2,979,528,incorporated herein by reference.

Generally, the polyoxybutylene-based block copolymers useful in thecompositions of the invention are prepared by first condensing 1,2butylene oxide with a water soluble organic compound initiatorcontaining 1 to about 6 carbon atoms such as 1,4 butylene glycol orpropylene glycol and at least 2 reactive hydrogen atoms to prepare apolyoxyalkylene polymer hydrophobe of at least about 500, preferably atleast about 1000, most preferably at least about 150 average molecularweight. Subsequently, the hydrophobe is capped with an ethylene oxideresidue. Specific methods for preparing these compounds are described inU.S. Pat. No. 2,828,345 and British Patent No. 722,746, both of whichare hereby incorporated by reference.

Useful polyoxybutylene based block copolymers conform to the followinggeneric formula:

    HO(C.sub.2 H.sub.4 O).sub.b (C.sub.4 H.sub.8 O).sub.a (C.sub.2 H.sub.4 O).sub.b H                                                (III)

wherein a is an integer such that the hydrophobe base represented by (C₄H₈ O) has a molecular weight of at least about 500, preferably at leastabout 1000 and most preferably at least about 3000, as determined byhydroxyl number, the polyoxyethylene chain constituting at least 60%,preferably at least 70% by weight of the copolymer, and the copolymerhaving a total average molecular weight of at least 5000, preferably atleast about 10,000, and most preferably at least about 15,000.

The copolymer is characterized in that all the hydrophobic oxybutylenegroups are present in chains bonded to an organic radical at the formersite of a reactive hydrogen atom thereby constituting a polyoxybutylenebase copolymer. The hydrophilic oxyethylene grops are used to cap thepolyoxybutylene base polymer.

Polyoxyethylene-polyoxypropylene block copolymers which can be used toform aqueous gels can be represented by the following formula:

    HO(C.sub.2 H.sub.4 O).sub.b (C.sub.3 H.sub.6 O).sub.a (C.sub.2 H.sub.4 O).sub.b H                                                (IV)

wherein a is an integer such that the hydrophobe base represented by (C₃H₆ O) has a molecular weight of at least about 900, preferably at leastabout 2500, most preferably at least about 4000 average molecularweight, as determined by hydroxyl number; the polyoxyethylene chainconstituting at least 60%, preferably at least 70% by weight of thecopolymer, and the copolymer having a total average molecular weight ofat least about 5000, preferably at least about 10,000, and mostpreferably at least about 15,000.

Polyoxyethylene-polyoxypropylene block copolymer adducts of ethylenediamine which can be used may be represented by the following formula:##STR1## wherein a and b are integers such that the copolymer may have(1) a hydrophobe base molecular weight of at least about 2000,preferably at least about 3000, and most preferably at least about 4500,(2) a hydrophile content of at least 60%, preferably at least 70% byweight, and (3) a total average molecular weight of at least about 5000,preferably at least about 10,000, and most preferably at least about15,000.

The hydrophobe base of the copolymer of formula V is prepared by addingpropylene oxide for reaction at the site of the four reactive hydrogenatoms on the amine groups of ethylene diamine. An ethylene oxide residueis used to cap the hydrophobe base. These hydrophile polyoxyethylenegroups are controlled so as to constitute at least 60%, preferably atleast 70% by weight, and most preferably at least about 80% by weight ofthe copolymer.

The procedure used to prepare aqueous solutions which form gels of thepolyoxyalkylene block copolymers is well known. Either a hot or coldprocess for forming the solutions can be used. A cold technique involvesthe steps of dissolving the polyoxyalkylene block copolymer at atemperature of about 5° to about 10° C. in water. When solution iscomplete the system is brought to room temperature whereupon it forms agel. If the hot process of forming the gel is used the polymer is addedto water heated to a temperature of about 75° C. to about 85° C. withslow stirring until a clear homogeneous solution is obtained. Uponcooling to room temperature, a clear gel is formed. Block copolymer gelscontaining polyoxybutylene hydrophobes must be prepared by the above hotprocess, since these will not liquify at low temperatures.

As used herein, the term "gel" is defined as a solid or semisolidcolloid containing a certain quantity of water. The colloidal solutionwith water is often called a "hydrosol".

The organic compound initiator which is utilized in the process for thepreparation of the polyoxyalkylene block copolymers generally is wateror an organic compound and can contain a plurality of reactive hydrogenatoms. Preferably, Y in formulas I and II above is defined as derivedfrom a water soluble organic compound having 1 to about 6 carbon atomsand containing x reactive hydrogen atoms where x has a value of at least2. Falling within the scope of the compounds from which Y is derived arewater soluble organic compounds such as propylene glycol, glycerin,pentaerythritol, trimethylolpropane, ethylene diamine, and mixturesthereof and the like.

The oxypropylene chains can optionally contain small amounts of at leastone of oxyethylene or oxybutylene groups. Oxyethylene chains canoptionally contain small amounts of at least one of oxypropylene oroxybutylene groups. Oxybutylene chains can optionally contain smallamounts of at least one of ethylene or oxypropylene groups. The physicalform of the polyoxyalkylene block copolymers can be a viscous liquid, apaste, or a solid granular material depending upon the molecular weightof the polymer. Useful polyoxyalkylene block copolymers generally have atotal average molecular weight of about 5000 to about 50,000, preferablyabout 5,000 to about 35,000 and most preferably about 10,000 to about25,000.

Preferably the polyoxyalkylene block copolymer is applied to surgicallyinjured tissue as an aqueous solution which upon contact with livingmammalian tissue forms a firm, adherent gel. Where an polyoxyalkyleneblock copolymer is a viscous liquid or paste, these compositions can beapplied without dilution to areas of surgical injury in the abdominal orthoracic cavities. Where the block copolymers have the physical form ofa paste or granular solid, it may be necessary or desirable toincorporate therewith either a low molecular weight liquid blockcopolymer, as defined herein, and/or a carrier liquid (solvent or adiluent).

The carrier solvent or diluent must be selected so as to bephysiologically acceptable. Water, glycerine, and sorbitol areacceptable as solvents for the block copolymers. Other possiblyacceptable solvents for the block copolymers are ethanol, isopropanol,n-butyl alcohol, tertiary butyl alcohol, cyclohexanone, hexylene glycol(2 methyl-2,4-pentanediol), butoxyethoxypropanol, butyl cellosolve®,butyl carbitol®, tetrahydrofuran, polyethylene glycols (liquid grades),polypropylene glycols having a molecular weight of less than 800,certain ketones, and propylene glycol. Generally, the block copolymersare insoluble in glycerol and mineral oil but these materials can beutilized as diluents, alone or in mixtures with the above solventsprovided such mixtures are acceptable physiologically for application toinjured tissue. Not all the above listed solvents for the blockcopolymers can be utilized in this invention since some of these may notbe physiologically acceptable for application to an injured tissue orotherwise.

The following examples illustrate the various aspects of the inventionbut are not intended to limit its scope. Where not otherwise specifiedthroughout this specification and claims, temperatures are given indegrees centigrade, and parts, percentages, and proportions are byweight.

EXAMPLE 1

An aqueous solution was made of a polyoxyethylene-polyoxypropylene blockcopolymer having the structure generically shown as formula IV andhaving a polyoxypropylene hydrophobe base average molecular weight ofabout 4000, a total average molecular weight of about 11,500, andcontaining oxyethylene groups in the amount of about 70% by weight ofthe total weight of copolymer. This copolymer is sold under thetrademark PLURONIC® F-127 by the BASF Corporation, Parsippany, N.J. Asolution was made by dissolving said polymer in cold (4° C.) distilledwater to give a concentration of 30% by weight in accordance with thecold process described above for forming aqueous solutions. Morespecific solution procedures are described in "Artificial Skin IPreparation and Properties of Pluronic F-127 Gels for Treatment ofBurns", J. Biomed. Mater. Res. 6, 527, 1972, incorporated herein byreference. The block copolymer has the formula: ##STR2##

This solution is a liquid at 4° C. and forms a gel which is adherent toliving tissue upon contact. This solution was applied at 4° C. in thefollowing experiments.

EXAMPLES 2-23

The following test procedure was utilized in order to determine theeffect of the solution of Example 1 on surgically injured rats.Twenty-two female Sprague-Dawley rats having a 300-400 gram body weightwere anesthetized with pentabarbital sodium (30 milligrams per kilogramof body weight) by application intraperitoneally through the left lumbarregion of the ventral abdominal wall. The abdomen was thereafter openedby a 5 centimeter midline vertical incision subsequent to cleansing ofthe abdominal surface with providone-iodine solution and removing hairby shaving. A one centimeter segment of each uterine horn was stipped ofserosa and an opposing one square centimeter of parietal peritoneum wasexcised, including the underlying muscle layer. Hemostasis was notattained.

Subsequently, the block copolymer solution of Example 1 was applied at atemperature of 4° C. to both the surgically injured area of the uterinehorn and the parietal peritoneum surgical injury but only on one side ofthe abdomen. After the first application had formed a gel, a secondlayer of block copolymer solution was applied. Approximately 0.5 to 1.5cubic centimeters of the block copolymer solution was applied dependingupon the amount necessary to adequately cover (on one side of theabdomen) both the surgically injured one centimeter segment of theuterine horn and the surgically injured one square centimeter area ofparietal peritoneal tissue.

The remaining side of the abdomen which was surgically injured in thesame manner was left untreated. The portion of the uterine horn whichwas stripped of serosa was then attached within 0.5 centimeter of thesurgical injury to the peritoneal parietal area by a single 3-0 VICRYLligature suture. This was done to insure that the injured surface of theuterine horn remained in close proximity to the surgical injury of theparietal area of the peritoneum until re-peritonealization had occurred.The abdominal wall was closed with a single layer of interrupted 0-0VICRYL suture and 21 days later each animal was sacrificed and theabdomen was examined for the presence of adhesions.

The following grading system was used to evaluate the results obtained:

0=no adhesion observed.

1=adhesions on 25% of the surgically injured area.

2=adhesions on 50% of the surgically injured area.

3=adhesions on 100% of the surgically injured area.

The tenacity of the adhesion which formed was evaluated according to thefollowing grading system.

0.0=no resistance to separation.

0.5=moderate force of separation required to rupture the adhesion.

1.0=strong force or cutting necessary for separation.

A rating for the results obtained was obtained by adding the results ineach of the grading systems. Results therefore would range from 0.0 to4.0 for each surgically injured area evaluated. The data were analyzedby a rank sum test and also by analysis of variance.

Since the bilaterally surgically injured areas of each rat were treatedwith block copolymer solution only unilaterally, each rat served as itsown control. Twenty of the 22 rats used in the evaluation survived a 21day period prior to sacrifice. Two animals died from failure toadequately close the abdominal incision to seal the peritoneal cavityand its contents.

Nineteen of the 20 surviving animals developed adhesions on theuntreated control side of the abdomen. The combined score for theuntreated control, including area and tenacity of the adhesions,averaged 3.2. On the block copolymer solution treated side of theabdomen, in 8 of the 20 surviving rats, some degree of adhesion wasnoted. The combined score, for the block copolymer treated areasincluding area and tenacity of adhesions in these 8 rats averaged only1.63. These results taken with the results for the block copolymertreated side of the remaining 12 rats having no adhesions provided acombined average score of only 0.7. This difference is consideredstatistically significant at the p less than 0.005 level.

EXAMPLES 24-46

The procedure of Examples 2-23 is repeated utilizing a 20% by weightaqueous solution of a polyoxybutylene-based block copolymer having thestructure generically shown as formula III and having a polyoxybutylenehydrophobe base having an average molecular weight of 3000 and a totalaverage molecular weight of 10,000. Substantially similar results areobtained following the test procedure of Examples 2-23.

EXAMPLES 47-69

Utilizing a 30% by weight aqueous solution of apolyoxyethylene-polyoxypropylene block copolymer having the structuregenerically shown in formula I and having a polyoxypropylene hydrophobebase molecular weight of 2000, a polyoxyethylene content of 70% byweight, and a total average molecular weight of 5000, the test procedureof Examples 2-23 is repeated to obtain substantially the same results.

EXAMPLES 70-92

The procedure of Examples 2-23 is repeated using a 30% by weight aqueoussolution of a polyoxyethylene-polyoxypropylene block copolymer adduct ofethylene diamine having a hydrophobe molecular weight of 1500 and atotal average molecular weight of 2500, said copolymer having ahydrophile content of 60% by weight and a total average molecular weightof 5500. Substantially similar results are obtained.

While this invention has been described with reference to certainspecific requirements embodiments, it will be recognized by thoseskilled in the art that many variations are possible without departingfrom the scope and spirit of the invention, and it will be understoodthat it is intended to cover all changes and modifications of theinvention, disclosed herein for the purposes of illustration, which donot constitute departures from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A process for reducingpost-surgical adhesion formation/reformation following surgical injuryto organs situated in the mammalian peritoneal or pleural cavity,comprising separating said organs from adjacent tissue with an effectiveamount of a composition comprising:a polyoxyalkylene block copolymer ofthe formula

    Y[(A).sub.n --E--H].sub.x                                  (I)

wherein A is an oxyalkylene moiety having an oxygen/carbon atom ratio ofless than 0.5, x is at least 1, Y is derived from water or an organiccompound containing x reactive hydrogen atoms, E is a polyoxyethylenemoiety, n has a value such that the average molecular weight of A is atleast about 500 to about 900, as determined by the hydroxyl number of anintermediate,

    Y[(A).sub.n --H].sub.x                                     (II)

and the total average molecular weight of the copolymer is at least5000.
 2. The process of claim 1 wherein Y in said formulas I and II is awater soluble organic compound having 1-6 carbon atoms, and saidcopolymer is selected from the group consisting of apolyoxyethylene-polyoxybutylene block copolymer, apolyoxyethylene-polyoxypropylene block copolymer and mixtures thereof,wherein the polyoxyethylene moiety constitutes at least 70% by weight ofthe polymer and wherein said composition includes a physiologicallyacceptable carrier liquid.
 3. The process of claim 2 wherein saidcopolymer is selected from block copolymers which form aqueous gels at aconcentration of about 10-40% by weight of the total weight of saidcomposition.
 4. The process of claim 3 wherein said Y is derived from acompound selected from the group consisting of propylene glycol,butylene glycol, glycerin, pentaerythritol, trimethylolpropane,ethylenediamine, and mixtures thereof, and said carrier liquid is water.5. The process of claim 4 wherein Y is derived from propylene glycol, Ais the residue of propylene oxide, and the intermediate of Formula IIhas an average molecular weight of at least about
 900. 6. The process ofclaim 4 wherein Y is derived from butylene glycol, A is the residue ofbutylene oxide, and the intermediate of Formula II has an averagemolecular weight of at least about
 500. 7. The process of claim 5 orclaim 6 wherein said polymer has the formula

    HO(C.sub.2 H.sub.4 O).sub.b (C.sub.4 H.sub.8 O).sub.a (C.sub.2 H.sub.4 O).sub.b H                                                (III)

wherein in III, a is an integer such that the hydrophobe baserepresented by (C₄ H₈ O) has a molecular weight of at least 1000, asdetermined by hydroxyl number, the polyoxyethylene chain constitutes atleast about 60% by weight of the copolymer, and the copolymer has atotal average molecular weight of at least 5,000, or

    HO(C.sub.2 H.sub.4 O).sub.b (C.sub.3 H.sub.4 O).sub.a (C.sub.2 H.sub.4 O).sub.b H                                                (IV)

wherein in IV, a is an integer such that the hydrophobe base representedby (C₃ H₆ O) has a molecular weight of at least about 1500 averagemolecular weight, as determined by hydroxyl number, the polyoxyethylenechain constitutes at least about 60% by weight of the copolymer, and thecopolymer has a total average molecular weight of at least 5,000 or##STR3## wherein in V a and b are integers such that the copolymer has ahydrophobe molecular weight of at least about 2000, a hydrophile contentof at least about 60%, and a total average molecular weight of at leastabout 5,000.
 8. The process of claim 7 wherein said copolymer is##STR4##
 9. The process of claim 8 wherein said copolymer is present isa concentration of about 15% to about 30% by weight of the total weightof said composition and said composition is a liquid at ambienttemperature and forms a gel upon contact with said mammalian tissue. 10.The process of claim 9 wherein said composition contains at least one ofa humectant, a bactericide, a bacteriostatic agent, an agent to preventleucocyte migration into an area of surgical injury, and a fibrinolyticagent.